Hydraulic composition

ABSTRACT

A hydraulic composition comprises a hydraulic component and an organic hydrogel, and optionally aggregate, a reinforcing material and other additives and has a slump value, determined by the testing method of JIS A1101, of not more than about 1 cm in a concrete formulation and a flow value, determined by the testing method of JIS R5201, of not more than about 120 mm in a mortar or paste formulation.

RELATED CASES:

This application is a divisional application of U.S. Ser. No. 07/249,248filed Sep. 26, 1988, now U.S. Pat. No. 4,883,535, which in turn is acontinuation of U.S. Ser. No. 07/050,338, filed May 18, 1987, nowabandoned.

This invention is a novel dry hydraulic composition, and morespecifically, a dry hydraulic composition containing a hydrauliccomponent and an organic hydrogel and optionally, aggregate, areinforcing material and other additives and a process for producing ahardened product which comprises compressing the hydraulic composition,molding it by vibration or application of a centrifugal force, etc. andthen hardening it.

In hardening a hydraulic component such as cement and gypsum, it is theusual practice to knead it with water and optionally aggregate and areinforcing material to form a slurry before it is actually applied. Inorder to improve the kneadability of the aqueous slurry and itsworkability at the time of application, water is used at this time in anamount much larger than the amount, calculated from stoichiometricproportions, of water which the hydraulic component requires. Thismethod, however, has various problems, such as a reduction of strength,an increase of bleeding water, a generation of sludge at the time ofcentrifugal molding, and a reduction of thawing resistance caused by theunhydrated water after setting.

When gypsum is used as the hydraulic component, hardening of gypsummixed with water begins rapidly. When it is used as an ordinary slurry,the time within which it can be cast is as short as 5 to 10 minutes, andit must be processed within a short period of time. This method alsorequires a drying step for evaporating the excess of water.

Furthermore, since the viscosity of the aqueous slurry is low,aggregate, reinforcing material, etc., are difficult to disperseuniformly in the slurry because of the difference in specific gravitybetween the aqueous slurry and the aggregate, the reinforcing material,etc. Thus, in order to ensure uniform mixing by using water in an amountrequired to harden the hydraulic binder in the production of buildingboards, there was proposed a method in which the mixing is carried outin a substantially dry condition using crushed ice or water frozen insnow form instead of water (Japanese Patent Publication No. 5694/1978).Recently, there was proposed a method in which the amount of water isdecreased by using crushed ice instead of water in the production ofconcrete (Research Report of Tokai Chapter of Japanese Society ofArchitecture, February 1986, page 41).

According to these methods, however, the temperature of the materialsand the temperature of the environmental atmosphere should be controlledso as not to permit melting of ice during kneading. Furthermore, sincethe particle diameter of ice has much to do with the uniform mixabilityof the hydraulic component with ice, the particle diameter of ice shouldbe controlled until the kneading is over, and the ice must also becontrolled before the kneading. When the mixture is hardened while theice still remains, those parts of the resulting hardened product whichare occupied by the ice are liable to become voids and reduce thestrength of the hardened product. Hence, the production of the hardenedproduct requires a different control from that in the prior art, and isunsuitable for industrial practice. Moreover, since the kneaded mixturehas a low temperature in the production of products in factories,hardening of the hydraulic component is retarded and the productivity isreduced.

On the other hand, a technique of adding a highly water-absorbing resinto a cement mixture is known (for example, Japanese Laid-Open PatentPublications Nos. 69257/1981 and 141450/1984). This technique isintended to reduce the effect of water in the cement mixture by causinga highly water-absorbing resin to absorb water existing in a largeamount in the cement mixture.

A technique of using a hydrogel as a source of supplying water has beenquite unknown in the past.

The present inventors have made extensive investigations in order tosolve the above problems of the prior art. These investigations have nowled to the discovery that mixing in a dry condition using an organichydrogel as a source of water supply can give a uniform kneaded mixtureof a hydraulic component having excellent dispersibility, and increaseits pot life, and that the resulting kneaded mixture can be hardenedwith a small amount of water to give a hardened product having highstrength.

Thus, according to this invention, there is provided a dry hydrauliccomposition comprising a hydraulic component and an organic hydrogel andoptionally aggregate, a reinforcing material and other additives.

The hydraulic component used in this invention denotes an inorganicmaterial which hardens by hydration reaction. Specific examples includecements such as ordinary portland cement, high early strength portlandcement, moderate heat-of-hardening portland cement, alumina cement, flyash cement, blast furnace cement, silica cement, slag cement, andvarious mixed cements; and hemihydrate gypsum (obtained by dehydratingdihydrate gypsums such as natural gypsum, gypsum as a by-product ofphosphoric acid production, gypsum as a by-product of titaniumproduction, and gypsum resulting from desulfurization of dischargedsmoke). The hydraulic component used in this invention also embracesblast furnace slag and siliceous materials such as fly ash and brickscraps which harden in the presence of an alkali stimulating agent.

The organic hydrogel used in this invention may be any gel-like organicmaterial which holds large amounts of water, for example, 5 to 1000times, preferably 10 to 800 times, its own weight of water. Specificexamples include hydrogels obtained by water absorption of highlywater-absorbing polymers such as starch/acrylonitrile graft copolymer,carboxymethyl cellulose, polyacrylonitrile, polyethylene oxide, vinylacetate/acrylic acid salt copolymer, vinyl alcohol/acrylic acid saltcopolymer, polyacrylic acid salts and olefin/maleic anhydridecopolymers; and hydrogels obtained by reacting poly(carboxylic acidsalts) such as poly(acrylic acid salts) and salts of olefin/maleicanhydride copolymers with crosslinking agents in the presence of water.

The type of such a highly water-absorbing resin is not particularlyrestricted, and those which are generally commercially available can beused.

The amount of the organic hydrogel to be mixed is usually that which cansupply water to be used. It is properly selected depending upon therequired properties of the final product or its use. Preferably, theamount of the organic material constituting the hydrogel is limited tonot more than 5 parts by weight per 100 parts by weight of the hydrauliccomponent. The organic hydrogel is in the form of, for example,particles, plates or rods. Its form is not restricted by the method ofuse, but in view of the ease of mixing, it is preferably in aparticulate form.

Water to be used is not particularly restricted. Usually, city water,underground water and sea water may be used.

The water content of the hydraulic composition of this invention islimited in order to maintain a dry condition. The water content differsdepending upon the materials used, their proportions, temperature, etc.and cannot be generalized. The upper limit of the water content isusually one in which the slump value is not more than about 1 cm (by thetesting method of JIS A 1101) in a concrete formulation, and one inwhich the flow value is not more than about 120 mm (by the testingmethod in JIS R 5201) in a mortar or paste formulation. Specifically, anordinary concrete formulation comprising ordinary portland cement,crushed stones and river sand has a water content of not more than about150 kg/m³. A mortar formulation with a cement/sand ratio of 1/2 has awater/cement ratio of not more than about 0.4. When the hydrauliccomponent is gypsum, the amount of water used is not more than 50% byweight, preferably not more than 40% by weight, based on the gypsum.There is no lower limit to the amount of water used. Usually, however,the amount of water is at least 3% by weight, preferably at least 10% byweight, based on the hydraulic component. The lower limit of the amountof water is much smaller than the stoichiometric proportion of thehydraulic component, but since the hydraulic component gradually forms ahydrate, a cured product can be produced from it with a small amount ofwater if during the aging period, required water is supplied fromoutside.

In addition to the hydraulic component and the organic hydrogel asessential ingredients, the composition of this invention may optionallycontain aggregate, reinforcing materials and other additives usuallyemployed in the art. Specific examples of the aggregate are sand,gravel, lightweight aggregate for example, sawdust, expanded perlite,calcined vermiculite, foamed polyurethane, foamed polystyrene, resinousmicroballoons (such as microballoons of phenolic resins, polyvinylidenechloride and epoxy resin), inorganic microballoons (volcanic rocks,silica sand, and sodium silicate)], weighting materials (steel balls andbaryte), clays, bentonite and lime. When gypsum is used as the hydrauliccomponent, the lightweight aggregate is preferably an inorganicmicroballoon.

Specific examples of the reinforcing materials include pulp fibers,glass fibers, rockwool, resin fibers, carbon fibers, aramid fibers andmetallic fibers.

The alkali stimulating agent used in this invention is a componentnecessary for blast furnace slag having latent hydraulic property or asiliceous material which undergoes pozzolan reaction to chemically reactto form a hardened product. Specific examples are oxides and hydroxidesof metals such as sodium, potassium, calcium, magnesium and aluminum,and portland cement which undergoes hydration reaction with water toform Ca(OH)₂. Slaked lime and portland cement are economicallyadvantageous.

The amount of the alkali stimulating agent mixed may be one required forthe hydraulic component to react, and is properly selected dependingupon the required properties or uses of the final product. For example,in a combination of granulated blast furnace slag and slaked lime as thealkali stimulating agent, the amount of slaked lime is 0.5 to 20 partsby weight per 100 parts of the granulated blast furnace slag. In acombination of the granulated blast furnace slag and portland cement asthe alkali stimulating agent, the amount of the portland cement is atleast 1 part by weight per 100 pats by weight of the granulated blastfurnace slag since the portland cement itself is hydraulic.

The siliceous material which undergoes pozzolan reaction such as fly ashis desirably mixed together with portland cement which undergoeshydration reaction to form Ca(OH)₂. The amount of the portland cementmixed for this purpose is at least 10 parts by weight but not exceeding1,000 parts by weight per 100 parts by weight of the siliceous material.Larger amounts are not economically advantageous.

Usually employed dispersants may be incorporated in the composition ofthis invention. Inclusion of a dispersant in at least part of theorganic hydrogel advantageously permits consolidation not only by anoperation under low pressure but also by an operation of vibration orthe like and thus gives a uniform hardened product.

The dispersants may be any of those used for hydaulic components such ascement and gypsum. Specific examples include water reducing agents,high-performance water reducing agents, and fluidizing agents, such asresin acid salts, ligninesulfonic acid salts, hydroxycarboxylic acidsalts, polyol complexes, melamine sulfonic acid/formalin condensate orits salts, creosote oil sulfonic acid/formalin condensate or its salts,naphthalenesulfonic acid/formalin condensate or its salts,polycarboxylic acids or their salts.

The amount of the dispersant used is properly chosen according to itstype or the properties required of the final product. Usually, it is0.01 to 3% by weight, preferably 0.05 to 1% by weight, based on thehydraulic component as solids.

A hydrogel containing the dispersant may be obtained by, for example,causing an aqueous solution of the dispersant to be absorbed by a highlywater-absorbing polymer, or reacting a polycarboxylic acid salt with acrosslinking agent in the presence of an aqueous solution of thedispersant. The amount of the organic hydrogel containing the dispersantmay be one in which the amount of water to be used and the requiredamount of the dispersant can be supplied. It can be properly selectedaccording to the required properties or uses of the final product.

The organic hydrogel containing the dispersant may at least partlycontain the dispersant. The proportion of the organic hydrogelcontaining the dispersant in the entire organic hydrogel may be properlyselected according to the type of the dispersant or the proportions ofthe materials used. In view of the properties of the final product, itis preferred to keep it at 30% by weight or more, especially 50% byweight or more.

Specific examples of the other additives include binders, air-entrainingagents, cement wetting dispersants, expanding agents, water-proofingagents, strength increasing agents, setting accelerators, settingretarders, and thickeners. If possible, the additives are usedpreferably by including them in a highly water-absorbing resinbeforehand.

The sequence of mixing the individual ingredients may be properly chosendepending upon the purpose for which the final product is used.Specifically, the hydraulic component and the organic hydrogel aremixed, and as required, the mixture is further mixed with aggregate, areinforcing material and other additives; or the organic hydrogel isfirst mixed with aggregate, a reinforcing material and other additives,and then the mixture is further mixed with the hydraulic component; orall of the ingredients are mixed simultaneously. Usually, the mixing maybe carried out by using a Hobart mixer (mixer equipped with a stirringrod and capable of planetary motion), a tilted mixer, a forced-mixingtype mixer and a pin mixer.

The resulting hydraulic dry composition is a mixture of solid particlesunlike an ordinary slurry-like composition fluidized with water. Thereis no particular restriction on the method of hardening thiscomposition. For example, press molding, vibration molding andcentrifugal molding may be applied. Press molding is effected by fillingthe composition in a form and then pressing it.

Pressing may be carried out by using a press, a roller, etc. Thepressure to be applied differs depending upon the hydraulic composition.Usually, it is at least 5 kg/cm², preferably at least 10 kg/cm². Thetime required for pressing varies depending upon the pressure applied,the formulation of the composition, etc. Usually, pressure is preferablycontinued for at least 30 seconds. Vibration molding is carried out byfilling the composition in a form.

As required, the composition is removed from the form, and then aged.The method of aging is not particularly limited, and specific examplesare underwater aging, aging in humid air, steam aging and autoclaveaging.

Usually, during aging, water gradually oozes out from the hydrogel andhardening proceeds in the presence of this water. Where the amount ofwater in the hydrogel is less than the theoretically required amount ofwater for hardening, water must be supplied from outside in the stage ofaging in order to obtain complete hardening.

The hardened product so obtained can be used in various applications. Itis especially useful as building materials such as panels, cement tiles,paving blocks, slates, flooring materials and blocks. Hardened gypsumproducts may also be used as porcelains and works of arts and crafts.

Thus, according to the present invention, by using the organic hydrogelas a source of water supply, a dry hydraulic composition can be obtainedwhich does not require complex temperature control, has gooddispersibility, and can be hardened with a low water content to providea hardened product having excellent quality.

The invention also has an advantage in regard to energy in that a dryingstep can be omitted in the production of gypsum products.

The following Examples and Referential Examples illustrate the presentinvention more specifically. Unless otherwise specified, all parts inthese examples are by weight.

REFERENTIAL EXAMPLE 1

Hydrogels (I) to (III) were prepared by causing the highlywater-absorbing resins indicated in Table 1 to absorb predeterminedamounts of water. These hydrogels were in the form of particles eachhaving a particle diameter of about 1 mm.

                  TABLE 1                                                         ______________________________________                                                Highly water-absorbing resin                                          Hydrous                   Amount   Water                                      gel       Type            (parts)  (parts)                                    ______________________________________                                        (I)       Polyacrylic acid-type                                                                         5        1500                                                 resin (*1)                                                          (II)      Starch-acrylic acid                                                                           5        1500                                                 graft copolymer (*2)                                                (III)     iso-Butylene/maleic                                                                           5        1000                                                 acid copolymer (*3)                                                 ______________________________________                                         (*1): AQUALIC, a tradename for a product of Japan Catalytic Chemical Co.,     Ltd.                                                                          (*2): SANWET, a tradename for a product of Sanyo Chemical Co., Ltd.           (*3): KI GEL, a tradename for a product of Kuraray Isoprene Co., Ltd.    

REFERENTIAL EXAMPLE 2

Seventy-three (73) parts of an 8% aqueous solution of polyethyleneglycol diglycidyl ether (EPOLIGHT 400E, a tradename for a product ofKyoeisha Oils and Fats Chemical Industry Co., Ltd.) was added to 144parts of an 8% aqueous solution of a sodium salt (neutralization degree0.78) of isobutylene/maleic anhydride copolymer (ISOBAM 10, a tradenamefor a product of Kuraray Isoprene Chemical Co., Ltd.), and they wereuniformly mixed. The mixture was poured into a stainless steel vesseland the vessel was sealed up to prevent water evaporation and heated for2 hours in an oven at 60° C. to perform crosslinking reaction. Theresulting hydrogel (IV) was in the shape of a rectangle having a size of50×50×10 mm.

EXAMPLE 1

In each run, 1,500 g of cement (Asano ordinary portland cement), 1,500 gof sand (Toyoura standard sand) and each of the hydrogels (I) to (IV) inan amount corresponding to each of the amounts of water indicated inTable 2 were mixed for 3 minutes by a Hobart mortar mixer. The flowvalue of the mixture was measured in accordance with JIS R 5201. Theresults are shown in Table 2. The mixture was then filled in a mortarform having a size of 5 cm diameter ×10 cm), and a predeterminedpressure indicated in Table 2 was applied to it for 5 minutes to producea molded article. The molded article was aged overnight in humid air at20° C., and its upper surface was finished in accordance with JIS A1132. The molded article was then removed from the form, and aged inwater at 20° C. for a predetermined period of time. The compressionstrength of the resulting hardened product was measured in accordancewith JIS A 1108.

For comparison, the above procedure was repeated except that water wasused in the same amount as contained in the hydrogel instead of thehydrogel, and the pressuring operation was omitted. The compressionstrength of the resulting hardened product was measured.

The results are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                                       Compression strength                                   Water content                                                                         W/C.sup.( *.sup.)                                                                 Flow value                                                                          Pressure                                                                           (kg/cm.sup.2)                              Run No.                                                                              Hydrogel                                                                           (g)     (parts)                                                                           (mm)  (kg/cm.sup.2)                                                                      3 days                                                                            7 days                                                                            28 days                            __________________________________________________________________________    Invention                                                                     1-1    (I)  375     25  No flowing                                                                          100  561 642 711                                1-2    (I)  525     35  118    10  390 478 603                                1-3    (II) 375     25  No flowing                                                                          100  550 640 712                                1-4    (III)                                                                              375     25  No flowing                                                                          100  555 645 700                                1-5    (IV) 375     25  No flowing                                                                          100  565 648 718                                Comparison                                                                    1-6    --   525     35  125   A uniform molded article was not                                              obtained, and strength measurement                                            was impossible.                                 1-7    --   600     40  200   --   303 405 541                                __________________________________________________________________________     .sup.(*.sup.) : Amount of water per 100 parts of cement                  

The results demonstrate that the hydraulic composition of this inventioncan be hardened with a low water content, and the resulting hardenedproduct has very high strength.

EXAMPLE 2

In each run, Example 1 was repeated except that 1,000 g of cement, 2,000g of sand and each of the hydrogels shown in Table 3 in an amountcorresponding to each of the amounts of water indicated in Table 3 wereused instead of the materials used in Example 1.

For comparison, the above procedure was repeated except that water wasused in the same amount as contained in the hydrogel instead of thehydrogel and the pressurizing operation was omitted.

The results are shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________                        W/C            Compression strength                                   Water content                                                                         (*) Flow value                                                                          Pressure                                                                           (kg/cm.sup.2)                              Run No.                                                                              Hydrogel                                                                           (g)     (parts)                                                                           (mm)  (kg/cm.sup.2)                                                                      3 days                                                                            7 days                                                                            28 days                            __________________________________________________________________________    Invention                                                                     2-1    (I)  150     15  No flowing                                                                          400  375 522 692                                2-2    (I)  200     20  No flowing                                                                          300  548 680 787                                2-3    (I)  250     25  No flowing                                                                          200  530 613 677                                2-4    (I)  300     30  No flowing                                                                          100  403 493 615                                2-5    (I)  350     35  108    20  363 444 570                                2-6    (II) 250     25  No flowing                                                                          200  532 615 680                                2-7    (III)                                                                              250     25  No flowing                                                                          200  528 610 672                                2-8    (IV) 250     25  No flowing                                                                          200  535 619 680                                Comparison                                                                    2-9    --   400     40  114   A uniform molded article was not                                              obtained, and strength measurement                                            was impossible.                                 2-10   --   450      45 150   --   238 341 458                                __________________________________________________________________________     (*): W/C is parts of water to 100 parts of cement.                       

The above results show that even when the proportion of the aggregateused is high, the composition can be hardened with a much lower watercontent than in the prior art, and the resulting hardened product hasvery high strength.

EXAMPLE 3

In each run, 1,000 g of cement, 2,000 g of sand, the hydrogel (I) in anamount corresponding to a water content of 250 g, and a predeterminedamount of reinforcing fibers were mixed for 3 minutes by a Hobart mortarmixer. The mixture was filled in a mortar form (5 cm diameter ×10 cm),and by applying a pressure of 50 kg/cm² to it for 5 minutes, a moldedarticle was produced. The molded article was aged overnight in humid airat 20° C., and removed from the form. The resulting hardened product wascut longitudinally, and the state of dispersion of the fibers at the cutsection was observed.

For comparison, the above procedure was repeated except that 450 g ofwater was used instead of the hydrogel, and the pressurizing operationwas omitted. The cut section of the hardened product was observed.

The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                Reinforcing material                                                                          State of the                                                               Amount     fibers at the                                 Run No.   Type       (g)        cut section                                   ______________________________________                                        Invention                                                                     3-1       Polyethylene                                                                              24        Uniformly dis-                                          fibers (*1)           persed on the                                                                 entire surface                                3-2       Steel fibers                                                                             210        Uniformly dis-                                          (*2)                  persed on the                                                                 entire surface                                Comparison                                                                    3-3       Polyethylene                                                                              24        Concentrated                                            fibers                on the upper                                                                  portion                                       3-4       Steel fibers                                                                             210        Concentrated                                                                  on the lower                                                                  portions                                      ______________________________________                                         (*1): BONFIX, a tradename for a product of Mitsui Petrochemical               Industries, Ltd.                                                              (*2): SHINKO FIBER, a tradename for a product of Kobe Steelmaking Co.,        Ltd.                                                                     

It is seen from the results obtained that in the compositions of thisinvention, the reinforcing material having a difference in specificgravity can be uniformly dispersed and good hardened products withlittle separation of the reinforcing fibers can be obtained.

EXAMPLE 4

In each run, cement (Asano ordinary portland cement), coarse aggregate(crushed stones having a maximum diameter of 20 mm), occurring in Oume,Japan, fine aggregate (river sand occurring in Ooi River, Japan) andhydrogel (I) containing a predetermined amount of water were mixed inaccordance with the formulation shown in Table 5 and then kneaded by aforced kneading mixer for 90 seconds. The slump of the mixture wasmeasured in accordance with JIS A 1101. Thereafter, the mixture wasfilled in a concrete form having a size of 10 cm diameter ×20 cm, and apredetermined pressure as shown in Table 5 was applied to it to producea molded article. The molded article was aged overnight in humid air at20° C., and its upper surface was finished in accordance with JIS A1132. The molded article was then removed from the form, and aged inwater at 20° C. for a predetermined period of time. The compressionstrength of the resulting hardened product was measured in accordancewith JIS A 1108.

For comparison, the above procedure was repeated except that water wasused in the same amount as contained in the hydrogel instead of thehydrogel and the pressurizing operation was omitted.

The results are shown in Table 5.

                                      TABLE 5                                     __________________________________________________________________________                                         Compression                                          Mixing  W/C S/A          strength                                             C   W   (parts)                                                                           (%)                                                                              Slump                                                                              Pressure                                                                           (kg/cm.sup.2)                            Run No.                                                                              Hydrogel                                                                           (parts)                                                                           (parts)                                                                           (**)                                                                              (*)                                                                              (cm) (kg/cm.sup.2)                                                                      7 days                                                                             28 days                             __________________________________________________________________________    Invention                                                                     5-1    (I)  320 100 31  38 No slump                                                                           200  485  603                                 5-2    (I)  320 125 39  38 No slump                                                                           100  504  631                                 5-3    (I)  320 150 47  38 0.5   50  451  584                                 Comparison                                                                    5-4    --   320 150 47  38 1.0  A uniform molded article was                                                  not obtained, and strength                                                    measurement was impossible.                   5-5    --   320 160 50  38 6.3  --   334  472                                 __________________________________________________________________________     (*): S/A is a percentage of volume of fine aggregate to volume of fine        aggregate plus volume of course aggregate.                                    (**): W/C is parts of water to 100 parts of cement.                      

The above results demonstrate that the hydraulic composition of thisinvention can be hardened with a low water content even in the case of aconcrete formulation, and the resulting hardened product has very highstrength.

EXAMPLE 5

In each run, 1,500 g of calcined gypsum (made by Yoshino Gypsum Co.,Ltd.) and each of the hydrogels (I) to (IV) in an amount correspondingto each of the amounts of water indicated in Table 6 were kneaded for 2minutes by a Hobart mortar mixer. The mixture was left to stand for apredetermined period of time shown in Table 6, and filled in a formhaving a size of 4×4×16 cm. By applying a pressure of 15 kg/cm² for 5minutes, it was molded and hardened. The hardened product wasimmediately removed from the form and its flexural strength andcompression strength were measured in accordance with JIS R 5201.

For comparison, the above procedure was repeated except that water wasused instead of the hydrogel, the pressurizing operation was omitted,and the gypsum slurry was heated in an oven at 60° C. for 10 minutes toobtain a hardened product.

The results are shown in Table 6.

                  TABLE 6                                                         ______________________________________                                                                  Standing                                                                      time   Compres-                                                      Water/   after  sion   Flexural                                       Hydro-  gypsum   kneading                                                                             strength                                                                             strength                              Run No.  gel     (*)      (min.) (kg/cm.sup.2)                                                                        (kg/cm.sup.2)                         ______________________________________                                        Invention                                                                     6-1      (I)     18       2      99     41                                    6-2      (I)     18       30     103    40                                    6-3      (I)     18       60     95     44                                    6-4      (I)     25       2      86     35                                    6-5      (I)     35       2      80     33                                    6-6      (II)    18       2      97     39                                    6-7      (III)   18       2      100    43                                    6-8      (IV)    18       2      105    45                                    Comparison                                                                    6-9      --      70       2      51     25                                    6-10     --      70       10     Solidified and could                                                          not be poured into                                                            the form.                                    ______________________________________                                         (*): Amount of water per 100 parts of gypsum.                            

It is seen from Table 6 that in the present invention, the pot life ofthe kneaded mixture increases greatly and it has excellent workability;that gypsum can be mixed with a low water content and the resultinghardened gypsum product has very high strength and high quality; andthat the drying step required in the prior art can be omitted to provideprocess and energy advantages.

REFERENTIAL EXAMPLE 3

In each run, each of the dispersants indicated in Table 7 and water weremixed in predetermined amounts to prepare an aqueous solution of thedispersant. The aqueous solution was caused to be absorbed by a highlywater-absorbing resin (AQUALIC, a tradename for a product of JapanCatalytic Chemical Co., Ltd.) to obtain each of hydrogels (V) to (IX).The resulting hydrogels were in the form of particles each having aparticle diameter of about 1 mm.

                  TABLE 7                                                         ______________________________________                                                                Highly water-                                         Dispersant                    absorbing                                       Hydrous             Amount   Water  resin                                     gel     Type        (parts)  (parts)                                                                              (parts)                                   ______________________________________                                        (V)     Resin acid-type                                                                            3       1497    7                                                (*1)                                                                  (VI)    Ligninsulfo-                                                                              15       1485   10                                                nate type (*2)                                                        (VII)   Naphthalene-                                                                              20       1480   12                                                sulfonic acid/                                                                formalin                                                                      condensate salt                                                               (*3)                                                                  (VIII)  Polycarboxylic                                                                            15       1485   10                                                acid salt (*4)                                                        (IX)    Polycarboxylic                                                                            25       1475   25                                                acid salt (*4)                                                        ______________________________________                                         (*1): VINSOL, a tradename for a product of Yamaso Chemical Co., Ltd.          (*2): POZZOLITH No. 70, a tradename for a product of Nisso Master Builder     Co.                                                                           (*3): MIGHTY 150, a tradename for a product of Kao Co., Ltd.                  (*4): WORK 500, a tradename for a product of Nippon Zeon Co., Ltd.       

REFERENTIAL EXAMPLE 4

Twenty parts of a 20% aqueous solution of polyethylene glycol diglycidylether (EPOLIGHT 400 E, a tradename for a product of Kyoei Oils and FatsChemical Industry Co., Ltd.), 20 parts of "WORK 500" and 120 parts ofwater were added to 40 parts of a 20% aqueous solution of a sodium salt(neutralization degree 0.78) of isobutylene/maleic anhydride copolymer(ISOBAM 10, a tradename for a product of Kuraray Isoprene Chemical Co.,Ltd.), and they were uniformly mixed. The mixture was poured into astainless steel vessel. The vessel was sealed up so as to prevent waterevaporation, and then heated in an oven at 60° C. for 2 hours to performcrosslinking reaction. The resulting hydrogel (X) was in the form of arectangle having a size of 50×50×10 mm.

EXAMPLE 6

In each run, 1,000 parts of cement (Asano ordinary portland cement),2,000 parts of sand (Toyoura standard sand) and each of the hydrogels(V) to (X) in an amount to provide 250 parts of water were mixed for 3minutes by a Hobart mortar mixer. The flow value of the mixture wasmeasured in accordance with JIS R 5201. The results are shown in Table2. The mixture was then filled in a mortar form having a size of 5 cmdiameter ×10 cm), and a predetermined pressure indicated in Table 8 wasapplied to it for 5 minutes to produce a molded article. The moldedarticle was aged overnight in humid air at 20° C., and its upper surfacewas finished in accordance with JIS A 1132. The molded article was thenremoved from the form, and aged in water at 20° C. for a predeterminedperiod of time. The compression strength of the resulting hardenedproduct was measured in accordance with JIS A 1108.

For comparison, the above procedure was repeated using a hydrogel (XI)prepared by causing the highly water-absorbing resin (AQUALIC) to absorbwater free from the dispersant to an absorption ratio of 300.

The results are shown in Table 8.

                                      TABLE 8                                     __________________________________________________________________________                               Compression strength                                           W/C.sup.( *.sup.)                                                                 Flow value                                                                          Pressure                                                                           (kg/cm.sup.2)                                      Run No.                                                                              Hydrogel                                                                           (parts)                                                                           (mm)  (kg/cm.sup.2)                                                                      3 days                                                                            7 days                                                                            28 days                                    __________________________________________________________________________    Invention                                                                     8-1    (V)  25  No flowing                                                                          130  525 610 672                                        8-2    (VI) 25  "     130  533 625 668                                        8-3    (VII)                                                                              25  "     130  540 642 688                                        8-4    (VIII)                                                                             25  "     130  538 630 671                                        8-5    (X)  25  "     130  528 602 665                                        Comparison                                                                    8-6    (XI) 25  "     200  530 613 677                                        __________________________________________________________________________     .sup.(*.sup.) : Amount of water per 100 parts of cement.                 

The results show that in the present invention, the hydrauliccomposition can be molded under a low pressure and hardened with a lowwater content, and a hardened product having high strength can beobtained.

EXAMPLE 7

A mortar obtained in accordance with Example 6 was filled in a mortarform having a size of 5 cm diameter ×10 cm. The form was placed on avibratory table with a vibration number of 3000 rpm and an amplitude of1 mm (V-B consistometer, made by Tokyo Measuring Instrument Co., Ltd.),and by applying vibration for 2 minutes, the mortar was consolidated toa molded article. It was hardened as in Example 6, and the compressionstrength of the resulting hardened product was measured.

For comparison, the same operation was repeated using hydrogel (XI)containing no dispersant.

The results are shown in Table 9.

                  TABLE 9                                                         ______________________________________                                                   Water W/C     Compression strength                                        Hydro-                                                                              content (*)     (kg/cm.sup.2)                                    Run No.  gel     (parts) (parts)                                                                             3 days                                                                              7 days                                                                              28 days                            ______________________________________                                        Invention                                                                     9-1      (V)     300     30    403   493   615                                9-2      (VI)    300     30    415   501   625                                9-3      (VII)   300     30    420   522   638                                9-4      (VIII)  300     30    418   517   630                                9-5      (X)     300     30    408   505   611                                Comparison                                                                    9-6      (XI)    300     30    A dense solid molded                                                          article was not obtained,                                                     and strength measure-                                                         ment was impossible.                           9-7      (XI)    400     40    250   363   477                                ______________________________________                                         (*): W/C is parts of water to 100 parts of cement.                       

The results show that in the present invention, the hydrauliccomposition can be consolidated by a vibrator, and hardened with a lowwater content, and a hardened product having high strength can beobtained.

EXAMPLE 8

In each run, cement (Asano ordinary portland cement), coarse aggregate(crushed stones having a maximum diameter of 20 mm), fine aggregate(river sand occurring in Ooi River, Japan) and hydrogel (VII) were mixedin accordance with the formulation shown in Table 10 and then kneaded bya forced-mixing type mixer for 90 seconds. The slump of the mixture wasmeasured in accordance with JIS A 1101. Thereafter, the mixture wasfilled in a centrifugal molding form having a size of 20 cm diameter ×30cm, and centrifugally molded for 4 minutes at 6 G and for 5 minutes at20 G. Then, the amount of sludge generated was measured. After molding,the molded article was left to stand for 4 hours, heated to 75° C. overthe course of 3 hours, maintained at this temperature for 4 hours,allowed to cool overnight, and then removed from the form. The productwas then aged at room temperature for 7 days. The compression strengthof the resulting hardened product was measured in accordance with JIS A1108.

For comparison, a slurry composition was prepared using 1.5%, based onthe amount of cement, of a high-performance water reducing agent (MIGHTY150, a tradename for a product of Kao Co., Ltd.), and the same operationas above was carried out on this composition, and the amount of sludgegenerated and the compression strength of the hardened product weremeasured.

The results are shown in Table 10.

                                      TABLE 10                                    __________________________________________________________________________                                    Amount of                                                                           Compres-                                            Mixing  W/C S/A     sludge                                                                              sion                                                C   W   parts                                                                             (%)                                                                              Slump                                                                              generated                                                                           strength                                       Hydrogel                                                                           (parts)                                                                           (parts)                                                                           (*) (*)                                                                              (cm) (ml)  (kg/cm.sup.2)                           __________________________________________________________________________    Invention                                                                            (VII)                                                                              320 100 31  38 No slump                                                                           None  716                                     Comparison                                                                           --   480 149 31  38 12.2 80    637                                     __________________________________________________________________________     (*): S/A is a percentage of volume of fine aggregate to volume of fine        aggregate plus volume of course aggregate.                                    (**): W/C is parts of water to 100 parts of cement.                      

The results show that in the present invention, a dense solid moldedproduct can be obtained by centrifugal molding while preventinggeneration of sludge during molding, and the resulting hardened producthas very high strength.

EXAMPLE 9

Run No. 8-4 of Example 6 was repeated except that a 6:4 mixture ofhydrogel (IX) containing the polycarboxylic acid-type dispersant andhydrogel (I) containing no dispersant was used instead of the hydrogelused in Run No. 8-4. Nearly the same results were obtained.

EXAMPLE 10

In each run, 500 g of calcined gypsum (made by Yoshino Gypsum Co.,Ltd.), a predetermined amount of lightweight aggregate (silica balloons,50% average particle diameter 48 microns; a product of Shikoku KakenIndustry Co., Ltd.) and each of the hydrogels (I) to (IV) in an amountcorresponding to the amount of water shown in Table 11 were kneaded for2 minutes by a Hobart mortar mixer. The mixture was filled in a formhaving a size of 4×4×16 cm, and molded and hardened by applying apressure of 50 kg/cm² for 5 minutes. The hardened product wasimmediately removed from the form, and its density and compressionstrength (JIS R 5201) were measured.

For comparison, water was used in the same amount as contained in thehydrogel instead of the hydrogel, and by the same operation, theresulting gypsum slurry was poured into a form. It was heated in an ovenat 60° C. for a predetermined period of time without a pressurizingoperation. The density and compression strength of the resultinghardened product were measured.

The results are shown in Table 11.

                                      TABLE 11                                    __________________________________________________________________________                Light-    Water/   Hardened product                                           weight    gypsum                                                                             Drying   Compression                                           aggregate                                                                           Water                                                                             (parts)                                                                            time                                                                              Density                                                                            strength                                  Run No.                                                                              Hydrogel                                                                           (g)   (g) (*)  (min.)                                                                            (g/cm.sup.3)                                                                       (kg/cm.sup.2)                             __________________________________________________________________________    Invention                                                                     11-1   (I)   50   100 20   0   1.29 99                                        11-2   (I)  100   100 20   0   1.05 91                                        11-3   (I)  150   100 20   0   0.87 83                                        11-4   (II) 150   100 20   0   0.88 84                                        11-5   (III)                                                                              150   100 20   0   0.85 80                                        11-6   (IV) 150   100 20   0   0.86 80                                        Comparison                                                                    11-7   (I)  --    100 20   0   2.10 103                                       11-8   --   --    350 70   10  1.12 50                                        11-9   --    50   350 70   Could not be molded                                                           because a slurry could                                                        not be prepared.                                   11-10  --    50   500 100  30  0.90 32                                        11-11   --  100   500 100  Could not be molded                                                           because a slurry could                                                        not be prepared.                                   11-12  --   100   700 140  60  0.73 20                                        __________________________________________________________________________     (*): Amount of water per 100 parts of gypsum.                            

Cut sections of the resulting hardened products were observed. In thehardened products of the invention, the lightweight aggregate wasuniformly dispersed throughout the hardened products, whereas thelightweight aggregate gathered locally in the upper portion in thehardened products of comparison (Runs Nos. 11-9 to 11-12).

The foregoing results demonstrate that in the present invention, thehydraulic component can be mixed with a low water content even when theamount of the lightweight aggregate is increased, and since thedispersibility of the lightweight aggregate is excellent, the resultinghardened products have very high strength, and lightweight gypsumproducts of high quality can be obtained. Furthermore, the drying steprequired in the prior art can be omitted, and this provides process andenergy advantages.

EXAMPLE 11

Example 10 was repeated except that foamed polystyrene (made by YukaBadische Co., Ltd.; expansion ratio 50; average particle diameter 0.5mm) or GAROLITE (made by Shiraishi Industry Co., Ltd.; silica balloon;average particle diameter 250 micrometers).

The results are shown in Table 12.

When the cross sections of the hardened products in accordance with thisinvention were observed, the lightweight aggregate was uniformlydispersed throughout the hardened products.

                                      TABLE 12                                    __________________________________________________________________________                Light weight   Water/                                                                             Hardened product                                          aggregate      gypsum    Compression                                                Amount                                                                             Water                                                                             parts                                                                              Density                                                                            strength                                 Run No.                                                                              Hydrogel                                                                           Type  (parts)                                                                            (g) (*)  (g/cm.sup.3)                                                                       (kg/cm.sup.2)                            __________________________________________________________________________    Invention                                                                     12-1   (I)  GAROLITE                                                                            200  100 20   0.96 78                                       12-2   (I)  Foamed                                                                              100  100 20   0.76 83                                                   polystyrene                                                       Comparison                                                                    12-3   (I)  --    --   100 20   2.10 103                                      __________________________________________________________________________     (**): Water/gypsum is parts of water to 100 parts of gypsum.             

The foregoing results show that in the present invention, even when thetype of the lightweight aggregate is changed, the dispersant isuniformly dispersed and lightweight gypsum products having high strengthcan be obtained.

EXAMPLE 12

Example 1 was repeated except that 1,500 g of granulated blast furanceslag (CERAMENT, a product of Daiichi Cement Co., Ltd.), 75 g of cement,1,575 g of sand, and each of the hydrogels indicated in Table 13 in anamount corresponding to each of the amounts of water indicated in Table13 were used as the materials. The flow values of the cement mixturesand the compression strengths of the hardened products were measured.

For comparison, the above procedure was repeated except that water wasused in the same amount as contained in the hydrogels instead of thehydrogels and the pressurizing operation was omitted.

The results are shown in Table 13.

                                      TABLE 13                                    __________________________________________________________________________                                       Compression                                            Water content                                                                         W/C.sup.( *.sup.)                                                                 Flow value                                                                          Pressure                                                                           strength (kg/cm.sup.2)                     Run No.                                                                              Hydrogel                                                                           (g)     (parts)                                                                           (mm)  (kg/cm.sup.2)                                                                      7 days                                                                              28 days                              __________________________________________________________________________    Invention                                                                     13-1   (I)  394     25  No flowing                                                                          100  245   362                                  13-2   (I)  551     35  110    20  202   311                                  13-3   (II) 394     25  No flowing                                                                          100  230   345                                  13-4   (III)                                                                              394     25  No flowing                                                                          100  241   353                                  13-5   (IV) 394     25  No flowing                                                                          100  233   358                                  Comparison                                                                    13-6   --   551     35  120   A uniform molded product was                                                  not obtained, and strength                                                    measurement was impossible.                     13-7   --   630     40  173   --   148   245                                  __________________________________________________________________________     .sup.(*.sup.) : Amount of water per 100 parts of (blast furnace slag +        cement)                                                                  

The foregoing results demonstrate that the hydraulic composition of thisinvention can be hardened with a low water content even when granulatedblast furnace slag is used as the hydraulic component, and the resultinghardened product has very high strength.

EXAMPLE 13

In each run, fly ash (see Table 14 below for its physical and chemicalproperties), cement (Asano ordinary portland cement), sand (Toyourastandard sand) and hydrogel (I) were mixed in the predetermined amountsindicated in Table 15. Otherwise, the same procedure as in Example 12was repeated.

                  TABLE 14                                                        ______________________________________                                        Physical and chemical properties of fly ash                                   ______________________________________                                        Specific gravity:      2.10                                                   Blaine value:          3420 cm.sup.2 /g                                       Unit water amount ratio:                                                                             100%                                                   Ignition heat loss:     1.4%                                                  Moisture content:       0.2%                                                  SiO.sub.2 :             61.4%                                                 Al.sub.2 O.sub.3 :      24.2%                                                 Fe.sub.2 O.sub.3 :      4.8%                                                  CaO:                    2.3%                                                  ______________________________________                                    

For comparison, the above procedure was repeated except that water wasused in the same amount as contained in the hydrogel instead of thehydrogel and the pressurizing operation was omitted.

The results are shown in Table 15.

                                      TABLE 15                                    __________________________________________________________________________                                                         Compression                     Hydro-                                                                            Fly ash                                                                           Cement                                                                             Sand                                                                             Amount of                                                                           Amount of                                                                           Fly ash +                                                                            W/C + F                                                                             Pressure                                                                           strength                                                                      (kg/cm.sup.2)            Run No.                                                                              gel (g) (g)  (g)                                                                              water (g)                                                                           fly ash (*1)                                                                        cement/sand                                                                          (*2)  (kg/cm.sup.2)                                                                      7 days                                                                             28                  __________________________________________________________________________                                                              days                Invention                                                                     15-1   (I) 750  750 1500                                                                             375   50    1/1    25    100  153  272                 15-2   (I) 600  900 1500                                                                             375   40    1/1    25    100  202  318                 15-3   (I) 600  900 1500                                                                             450   40    1/1    30     50  165  279                 15-4   (I) 450 1050 1500                                                                             375   30    1/1    25    100  235  366                 15-5   (I) 450 1050 1500                                                                             450   30    1/1    30     50  191  317                 Comparison                                                                    15-6   --  600  900 1500                                                                             600   40    1/1    40    --    95  188                 15-7   --  450 1050 1500                                                                             450   30    1/1    30    A uniform molded article                                                      was                                                                           not obtained, and                                                             strength                                                                      measurement was                                                               impossible.                   15-8   --  450 1050 1500                                                                             600   30    1/1    40    --   127  246                 __________________________________________________________________________     (*1): Amount of fly ash: fly ash/(fly ash + cement)                           (*2): W/C + F: Amount of water per 100 parts by weight of (fly ash +          cement)                                                                  

The results show that in the present invention, the hydrauliccomposition can be hardened with a low water content, and the resultinghardened product has very high strength, and that to obtain the samestrength, inexpensive fly ash can be incorporated in a great amount toeconomical advantage.

EXAMPLE 14

Example 1 was repeated except that 1,500 g of blast furnace slag, 375 gof hydrogel (I), 1,500 g of sand and each of the amounts indicated ofeach of the alkali stimulating agents shown in Table 16 were used as thematerials.

For comparison, the above operation was repeated except that water wasused in the same amount as contained in the hydrogel instead of thehydrogel and the pressurizing operation was omitted.

The results are shown in Table 16.

The results given in Table 16 show that the hydraulic composition ofthis invention can be hardened with a low water content even when blastfurnace slag is used together with the alkali stimulating agent, and thehardened product obtained has very high strength.

                                      TABLE 16                                    __________________________________________________________________________                        Alkali                                                                        stimulating                                                                   agent                                                                 Water                                                                             W/C      Amount          Compression strength                             content                                                                           (parts)  (parts)                                                                            Flow value                                                                          Pressure                                                                           (kg/cm.sup.2)                        Run No.                                                                              Hydrogel                                                                           (g) (*1)                                                                              Type (*2) (mm)  (kg/cm.sup.2)                                                                      7 days                                                                              28 days                        __________________________________________________________________________    Invention                                                                     16-1   (I)  375 25  NaOH 10   No flowing                                                                          100  233   357                            16-2   (I)  375 25  Ca(OH).sub.2                                                                        5   No flowing                                                                          100  212   323                            16-3   (I)  375 25  Ca(OH).sub.2                                                                       10   No flowing                                                                          100  248   360                            16-4   (I)  375 25  Al(OH).sub.3                                                                       10   No flowing                                                                          100  225   320                            Comparison                                                                    16-5   --   375 25  NaOH 10   No flowing                                                                          A uniform molded product was                                                  not obtained, and strength                                                    measurement was impossible.               16-6   --   600 40  NaOH 10   168   --   115   208                            16-7   --   375 25  Ca(OH).sub.2                                                                       10   No flowing                                                                          A uniform molded product was                                                  not obtained, and strength                                                    measurement was impossible.               16-8   --   600 40  Ca(OH).sub.2                                                                       10   175        125   228                            16-9   --   375 25  Al(OH).sub.3                                                                       10   No flowing                                                                          A uniform molded product was                                                  not obtained, and strength                                                    measurement was impossible.               16-10  --   600 40  Al(OH).sub.3                                                                       10   170        119   215                            __________________________________________________________________________     (*1): Amount of water per 100 parts of blast furnace slag                     (*2): Amount of the alkali stimulating agent per 100 parts of blast           furnace slag                                                             

What is claimed is:
 1. A process for producing a hardened productcomprising:mixing a hydraulic component, an organic hydrogel holding 5to 1000 times its own weight of water, and optionally, aggregate, areinforcing material selected from the group consisting of pulp fibers,glass fibers, rockwool, resin fibers, carbon fibers and metallic fibers,and other additives selected from the group consisting of binders,air-entraining agents, cement wetting dispersants, expanding agents,water-proofing agents, strength increasing agents, setting accelerators,setting retarders and thickeners together to form a hydrauliccomposition; molding said hydraulic composition by pressurization undera pressure of at least 5 kg/cm² for at least 30 seconds, vibration orapplication of a centrifugal force; and hardening said molded hydrauliccomposition.
 2. The process of claim 1, wherein said molding is carriedout by pressurization.
 3. The process of claim 1, wherein said hydrauliccomponent is a cement.
 4. The process of claim 1, wherein said hydrauliccomponent is gypsum.
 5. The process of claim 1, wherein said hydrauliccomponent is blast furnace slag containing an alkali stimulating agent.6. The process of claim 1, wherein said hydraulic component is fly ashcontaining an alkali stimulating agent.
 7. The process of claim 1,wherein said organic hydrogel is obtained by water absorption of highlywater-absorbing polymers selected from the group consisting ofstarch/acrylonitrile graft copolymer and olefin/maleic anhydridecopolymers or obtained by reacting a polycarboxylic acid salt selectedfrom the group consisting of polyacrylic acid salts and olefin/maleicanhydride copolymer salts with a crosslinking agent in the presence ofwater.